Retractable undercarriage for airplanes



y 5, 1964 P. M. J. LALLEMANT 3,131,891

RETRACTABLE UNDERCARRIAGE FOR AIRPLANES Filed Feb. 19, 1962 2Sheets-Sheet 1 Fig.1

I INVENTUR ATTORNEY y 1954 P. MQJ. LALLEMANT 3,

RETRACTABLE UNDERCARRIAGE FOR AIRPLANES Filed Feb. 19, 1962 2Sheets-Sheet 2 INVENTOR ATTORNEY United States Patent "ice r. 3,131,891RETRACTABLE UNDERCARRIAGE FOR Pierre Martin Joseph Lallemant,Pott-Marly, France, as- "signo'r to Societe Hispano Suiia Lallemant,Rois-Colomb'es,'Fran'ce, aspciety'of'Fr'ance v Filed-Feb. 19, '1962,Ser. No. 173,953 Claimspriority, application FranceAiig. s, 1951 3Claims. "'(Cl. 244-402) V The present invention relates toundercarriages for airplanes, comprising'struts'to be retractedindividually into the airframe'of the airplane, for instance into thefuselageor into nacell'e's incorporated in the wings 'of the airplane.The invention is more'e's p'ecially but'notexclusively concerned withairplanes'of the 'high'wing type, wherethe struts of the main landinggear are to be retracted 'into nacelles incorporated in the high wing'ofthe airplane.

The chief object of this invention is to provide an undercarriage of theabove mentioned type which is better adapted to meet the requirements ofpractice than those known up to this-time,'in particular'concerning thespace that is occupied in retracted position.

This invention fela'fe's to the case where the undercarriagecomp'risesat -leastoiies'trut including a shockabsorber pivoted at its lower endto the support of the wheel belonging to said strut and at its upper endto a rigid connecting member disposed substantially in verticalalinement with said shock-absorber and itself pivoted to the airframe ofthe airplane and the invention is characterized in that retraction ofsaid strut is obtained by means of at least one telescopic fluidactuator the ends of which are pivoted respectively to the airframe ofthe airplane and to said rigid connecting element.

A prefered embodiment of this invention will be here after describedwith reference to the appended drawings, given merely by way of example,and in which:

FIG. 1 is a side view of an undercarriage according to the invention,shown in the down position;

FIG. 2 is a similar view showing the undercarriage in partly retractedposition;

FIG. 3 is a similar view showing the undercarriage "in wholly retractedposition.

In the embodiment of the invention illustrated by the drawings anundercarriage is intended to be retracted into a nacelle 1 incorporatedin one of the half-wings of the airplane.

The main strut of the undercarriage comprises a shockabsorber 2,preferably an oleo-pneumatic shock-absorber of the telescopic type, thelower end of which is pivoted at A to the support of wheel (of pair ofwheels) 3 corresponding to this strut and the upper end of which ispivoted at B to a rigid connecting element 4 extending substantially inline with said shock-absorber 2 when the undercarriage is in the downposition, this element 4 being itself pivoted at C to the airframe ofthe airplane. Preferably pivot points A, B and C are at leastapproximately located on a vertical line when the undercarriage is inthe down position.

In the embodiment of the invention illustrated by the drawings,interconnecting element 4 is in the form of a piece having a generaltriangular outline.

Wheel support 5 is preferably arranged, as shown, so that theundercarriage is of the so-called indirect type, said supportconsisting, as shown, of a lever 5 at one end of which wheel 3 isjournalled. To the other end of lever 5 there is pivoted, at B, a rod 6the upper end of which is pivoted at E to the airframe of the airplane.Said rod 6 is connected to element 4 through a rigid link 7 one end ofwhich is pivoted at F to an intermediate 3,131,891 Patented May 5, 1

point of rod G'and'the other end of which is pivoted to element 4at a'point G. Preferably, a's shownby the drawings, this'point'G'isloca ted,with respect to'line A, B, C, 'onthe sidethereofopposed to that towardwhich wheel3'is to'be lifted. The point A where 's'hock absorber 2 ispivoted 'to the wheel supporting lever 5 is located b etweenthe ends ofsaid lever '5.

Now, according 'to the main feature of thisinvention, retraction of theund erc'arria'geis effected byr'neans of at leastone fluid actuator,preferablya hydraulic one, one of the ends of which is pivoted to theairframe and the 'otherend of which is pivoted to connectinglement 4,this'actuator8, which is preferably of the double "acting'type,'b'eingarranged in "such manner that, during the retraction operation, it"causes connecting element "4, "to pivotaboutpoint C in adirection suchthat this move ment produces an'upward'rtraction "of the deformablesystem A, B, C, D, E, F.

Preferably, in order to reduce as much as possible the space occupied bythe undercarriage in retracted pbsi tion, actuator S is mountedrso as toexert 'a pulling thrust during the retraction of the undercarriage; "Forthis purpose sai d actuator must be located, with respect to line A, B,C, on the side thereof opposed to that toward which wheel 3 must bemoved upwardly. Actuator 8 is pivoted at one end, at H, to the airframeand at I to connecting element 4.

When comparing FIG. 2 (partly retracted position) and FIG. 3 (whollyretracted position) with FIG. 1 the following points should be noted:

(a) retraction of the undercarriage is accompanied by a substantialreduction of its length so that the space necessary for housing theretracted undercarriage is reduced with respect to the relatively greatheight of this undercarriage in the down position, made necessary by thefact that the wing is a high wing;

(12) the whole of the lifting mechanism is constantly located in areduced space extending approximately above the corresponding wheel,which has but a small displacement in the longitudinal direction of theairplane during the retraction operation; and

(c) actuator 8, due to the substantial alinement of points A, B, Cwithstands practically but a small portion of the efforts applied to thewheel when the aircraft is taxiing on the ground.

Of course the undercarriage above described may be fitted with allsuitable safety devices, such for instance as a device for locldng theundercarriage in the down position (acting for instance upon theactuator), an electric signalling device operated by the locking deviceand indicating to the pilot that the undercarriage is truly in downposition for landing, a device for cutting OK the feed of liquid to theactuator when the undercarriage is in the down position and so on.

Of course the invention is not limited to the particular embodimentthereof shown by the drawings.

What I claim is:

1. For use with an airplane fixed structure, an undercarriage unit whichcomprises, in combination, a rigid member pivoted to said airplanestructure about a single first axis transverse to the fore-and-aftdirection of the airplane, a wheel, a rigid wheel support, a shockabsorbing strut pivoted at one end to said rigid member about a singlesecond axis and at the other end to said wheel support about a singlethird axis, respectively, both of said second and third axes beingtransverse to the foremovable with respect to each other, one of saidelements being pivoted to said airplane structure and the other of saidelements being pivoted to said rigid member about a fourth single axisand a fifth single axis, respectively, both transverse tothe'fore-and-taft direction of the airplane, said wheel support being alever pivotable about said third axis, saidwheel being journalled insaid lever at one end thereof, a rod pivoted at one end to the saidlever andtat the other end directly to said airplane structure aboutrespective axes transverse to the fore-and-aft direction 'oftheairplane, and a rigid link pivoted "at one end toan intermediate pointof said rod and at the other end to said rigid member about respectiveaxes transverse to the fore-and-aft direction of the airplane. 2;. Foruse with an'airplane fixed structure, an undercarriage unit whichcomprises, in combination, a rigid 7 member pivoted to said airplanestructure about a single first axis'transverse to the fore-and-aftdirection of the airplane, a wheel, a rigid wheel support, ashock-absorbing strut pivoted at one end to said rigid member-about v asingle second axis and at the other end to said wheel support about asingle third axis, respectively, both of versely tthereto when th eundercarriage unit is in the movable with respect to each other, one ofsaid elements being pivoted to said airplane structure and the other ofsaid elements being pivoted to said rigid member about a single fourthaxis and a single fifth axis, respectively, both transverse to thefore-and-aft direction of the airplane, said wheel support being a leverextending on oppothe airplane, said first, second andthird axes being10-" V cated in a common vertical plane transverse to the -foreand-aftdirection of the airplane when the undercarriage is in-the downposition.

3. An undercarriage according 'to claim -2 wherein I said hydraulicactuator is located, with respect to the common plane of the first,second and third axes, on the side thereof opposed to that toward whichsaid wheel i is moved upwardly when the undercarriage is retracted.

down position, a hydraulic actuator for retracting said I strut, saidactuator including two elements telescopically References Cited in thefile of this patent V UNITED STATES PATENTS 2,506,178 I Shaw May 2,1950' 2,982,500 Lucien Ma a, 1961

1. FOR USE WITH AN AIRPLANE FIXED STRUCTURE, AN UNDERCARRIAGE UNIT WHICHCOMPRISES, IN COMBINATION, A RIGID MEMBER PIVOTED TO SAID AIRPLANESTRUCTURE ABOUT A SINGLE FIRST AXIS TRANSVERSE TO THE FORE-AND-AFTDIRECTION OF THE AIRPLANE, A WHEEL, A RIGID WHEEL SUPPORT, A SHOCKABSORBING STRUT PIVOTED AT ONE END TO SAID RIGID MEMBER ABOUT A SINGLESECOND AXIS AND AT THE OTHER END TO SAID WHEEL SUPPORT ABOUT A SINGLETHIRD AXIS, RESPECTIVELY, BOTH OF SAID SECOND AND THIRD AXES BEINGTRANSVERSE TO THE FOREAND-AFT DIRECTION OF THE AIRPLANE, SAID STRUTEXTENDING ALONG A LINE INTERSECTING SAID FIRST AND SECOND AXESTRANSVERSELY THERETO WHEN THE UNDERCARRIAGE UNIT IS IN THE DOWNPOSITION, A HYDRAULIC ACTUATOR FOR RETRACTING SAID STRUT, SAID ACTUATORINCLUDING TWO ELEMENTS TELESCOPICALLY MOVABLE WITH RESPECT TO EACHOTHER, ONE OF SAID ELEMENTS BEING PIVOTED TO SAID AIRPLANE STRUCTURE ANDTHE OTHER OF SAID ELEMENTS BEING PIVOTED TO SAID RIGID MEMBER ABOUT AFOURTH SINGLE AXIS AND A FIFTH SINGLE AXIS, RESPECTIVELY, BOTHTRANSVERSE TO THE FORE-AND-AFT DIRECTION OF THE AIRPLANE, SAID WHEELSUPPORT BEING A LEVER PIVOTABLE ABOUT SAID THIRD AXIS, SAID WHEEL BEINGJOURNALLED IN SAID LEVER AT ONE END THEREOF, A ROD PIVOTED AT ONE END TOTHE SAID LEVER AND AT THE OTHER END DIRECTLY TO SAID AIRPLANE STRUCTUREABOUT RESPECTIVE AXES TRANSVERSE TO THE FORE-AND-AFT DIRECTION OF THEAIRPLANE, AND A RIGID LINK PIVOTED AT ONE END TO AN INTERMEDIATE POINTOF SAID ROD AND AT THE OTHER END TO SAID RIGID MEMBER ABOUT RESPECTIVEAXES TRANSVERSE TO THE FORE-AND-AFT DIRECTION OF THE AIRPLANE.